Wow -- is he sure about this? The guy is only 35 and has probably dated only 98 percent of Hollywood. There are probably a couple of women left that he hasn't tried yet.

The singers' relationship began last summer and was on and off for a spell. But by the holidays, they were reportedly inseparable. A source has told HollywoodLife.com that Mayer wants to co-habitate.

"John wants to take his relationship with Katy to the next level," the source said. "He has suggested to Katy that they get a place of their own. He feels like she's the one for him and wants to commit himself fully."

Let me check the calendar here ... nope, it's not April 1.

Perry, 28, was previously married to actor Russell Brand. Mayer, of course, hasn't just been around the block -- he constructed his own block, dating big names like Jennifer Aniston, Taylor Swift and Jessica Simpson.

No word yet as to where the two may be house hunting, but Mayer even went so far as to call their future home "a sanctuary," according to HollywoodLife.com.